Internal combustion engines of the reciprocating piston type may have crankcase structures which permit a limited degree of sidewall movement, or torsional distortion, under the operational stresses imposed by the motion of the pistons and crankshaft. Such crankcase sidewall movement may produce undesirable vibration and radiated sound in certain automotive applications.
Cross bolting of the engine main bearing caps to the sidewalls of the crankcase has been shown to reduce such distortion and vibration. U.S. Pat. No. 5,218,938 issued Jun. 15, 1993, in the name of Miller et al., discloses such a bearing cap utilized to increase the rigidity of the base engine structure by integrating a structural oil pan assembly with the engine block.
Bearing caps typically suffer from a structural limitation brought about by typical crankcase design limitations and as a result of the method commonly employed in their manufacture which require that the caps have bodies with substantially parallel side surfaces extending the length thereof. The resultant straight sided bearing cap structure is prone to torsional movement and vibration.